Plant Science London Field Course

The day started with a tour of the Royal Botanical Gardens at Kew (RBG Kew)and their herbarium. The herbarium contains 7 million specimens of approximately 140,000 plant species. Jurriaan de Vos guided us through the various labyrinth like system of purpose built herbaria. Jurriaan had recently been on a research and sample collecting mission to Peru where he and his colleagues identified two new species as well as recorded first occurrences of plants in Peru.

The first room we entered was purpose built as a herbarium in the 1800s, now it is considered outdated as the temperature is variable and the cupboard doors can let insect pests in. The building has landmark status and so refurbishment cannot take place. The next herbarium had a lower ceiling as it was built after the invention of electric lighting and so tall windows were not required for natural light. The next room we were shown was the ‘post’ room where samples were prepared for sending to other institutions or were treated by freezing (72hr at -40oC) when returned from them. There has been a decline in material being sent out of Kew over recent decades due to the scanning of samples and genetic identification of plants. The last room was a contemporary herbarium, built to ideal specifications with a constant temperature of 15oC and a monitored relative humidity. This room was used to store plant samples such as from the legume family which are preferentially targeted by pests.

Students in the herbarium at Kew (Image: Eoin Lettice)

The fungarium boasts 1.3 million fungal specimens accounting for 60% of all known fungal diversity. The store is separated into UK fungi and the rest of the world. Fungal specimens from the UK are stored separately as they their care takes priority in the case of disasters such as fire. In addition amateur UK mycologists spend a lot of time with the UK specimens. The taxonomy of the fungarium is however 20 years out of date owing to recent advanced in genetic classification.

Fungi can happily reproduce asexually resulting in the same species of fungi being identified as two separate species, this confusion has been recently readjusted thanks to genetic analysis. There are the equivalent of 27’000 “sexes” with regards to fungi, compatibility is assessed at contact between mychorrhizae which is followed by either successful reproduction or “war”. Fungi are in fact closer to animals than plants with their cell walls comprising of chitin rather than cellulose. Investigation into commercial fungal products has yielded fungal leather substitute and a milk made by a fungus which has the gene for milk protein inserted into it.

The fungarium at Kew (Image: Eoin Lettice)

Melanie Jayne Howes presented a lecture on the use of plant natural products and plant chemicals in the treatment of Alzheimer’s. Alzheimer’s is a degenerative neurological disease caused by a deficiency in the production of acetylcholine. One option of treatment would be to find a similar compound to acetylcholine in plant products and apply these to medicine. This was done and the chemical Anecoline was effective at treatment but caused severe side effects such as convulsion and extreme nausea. Alternatively Physostigma venesquosum (Calabar bean) was used to stop the breakdown of acetylcholine as it contains toxic alkaloids which produce this effect. The problem was P. venesquosum also caused severe adverse effects in patients. The solution was found in Narcissus sp. and Galanthus sp. Which produce a drug now known as Galantamine which shows high levels of efficacy in the treatment of Alzheimer’s. Two of the four drugs currently on the market for the treatment of Alzheimer’s are plant derived. Plants also noted for their neurologically strengthening effects include Ginko biloba (250 year old specimen in Kew), rosemary, lemon balm, Lemon verbena and sage as well as Withania somnifera.

Bootstrap DNA by Charles Jencks at Kew (Image: Eoin Lettice)

Orchid conservation is conducted at Kew with a large focus on four species of orchid. One of these orchids is Cypripedium calceolus which can only be germinated if done so in conjunction with the particular fungal species. The seed coat is removed and fungal hyphae allowed to colonise the seed resulting in high and unprecedented rates of orchid germination in vitro. Orchid seeds are very small and germination is easier when they are fresh, chemical and physical germination inhibitors thwart germination attempts in mature seed.

At the end of the day I enjoyed resting my legs under the cherry blossom in the Japanese garden. I also enjoyed the tropical humidity in the Palm house which contained ten metre high banana plants, shrubs with blue cheese smelling green flowers as well as the oldest potted plant in the world a cycad at 250 year old!